add const

include/sp/common/ByteSwapping.h

@@ -16,7 +16,7 @@ void SwapBytes(T& value) {
 	std::reverse(ptr, ptr + sizeof(T));
 }
 
-bool IsSystemBigEndian() {
+static bool IsSystemBigEndian() {
 	static constexpr std::uint16_t test = 10;
 	static const bool isBigEndian = reinterpret_cast<const std::uint8_t*>(&test)[1] == 10;
 	return isBigEndian;